"Today, Marc Short, Chief of Staff to the Vice President, tested positive for COVID-19, began quarantine and assisting in the contact tracing process," Devin O'Malley, press secretary for the vice president, said in a statement, ABC News reported.
O'Malley said both Pence and wife Karen Pence tested negative for the virus on Saturday.
ABC News has also learned at least one additional staffer in the vice president's office has tested positive in the last few days and several staffers are now quarantining.
Pence has been crisscrossing the country on the campaign trail for weeks. He made visits to Lakeland and Tallahassee, Florida, on Saturday. On Friday, he spent time in his home state of Indiana, where he voted in person in Indianapolis, before holding rallies in Ohio and Pennsylvania. He will continue his schedule, O'Malley said, despite the close contact with Short.
"While Vice President Pence is considered a close contact with Mr. Short, in consultation with the White House Medical Unit, the Vice President will maintain his schedule in accordance with the CDC guidelines for essential personnel," he wrote in a statement.
The Centers for Disease Control and Prevention advise essential workers who have been exposed to COVID-19 should take their temperature before work, wear a face mask at all times and social distance "as work duties permit". Pence is scheduled to hold a rally in Kinston, North Carolina, on Sunday evening.
Short has served as Pence's chief of staff since March 2019.
Obst, a top political aide to the vice president, tested positive last week, multiple sources familiar with the matter told ABC News. He is an outside adviser and not a government employee.
He was spotted at a fundraiser at Trump Doral attended by both Pence and President Donald Trump on October 15. While he was traveling with the VP last week, he wasn't in close proximity to him, sources say.
Obst did not respond to a request for comment. The vice president's office did not immediately respond.
The trusted adviser, who ran Pence's campaign in 2016, has kept up a steady stream of tweets and retweets on Twitter in recent days and weeks, though he does not appear to have mentioned his own diagnosis.
This is the second time someone close to Pence has tested positive for the virus. Katie Miller, Pence's press secretary and wife of Trump adviser Stephen Miller, tested positive for COVID-19 in May.
Both Mike Pence and the second lady tested negative for coronavirus in the days after President Trump tested positive and was hospitalized at the beginning of October.
Earlier this month, in an interview with CNN, Short said the vice president was tested "every day".
At least 34 people connected to the White House tested positive for the virus earlier this month, including the president and first lady Melania Trump, as well as Press Secretary Kayleigh McEnany, campaign manager Bill Stepien, senior adviser for policy Stephen Miller and outside advisers Kellyanne Conway and Chris Christie.